Current-time behaviour for copper electrodeposition. II. Experimental examination of surface diffusion and direct incorporation models at hemispherical sites

The surface diffusion model has been examined by the measurement of current-time transients for copper electrodeposition on to a polycrystalline copper electrode in acidic copper sulphate solution. The results did not satisfy the surface diffusion model criteria. The current-time profiles showed a linear dependence on 1/t^1/2 except at high overpotentials. This behaviour could be explained by a direct incorporation model at hemispherical sites through a hemispherical diffusion layer. A parameter characterizing this model, the number of sites, was estimated to be of the order of 10⁴ cm^–2.